Phonograph drive



United States Patent 3,445,117 PHONOGRAPH DRIVE Henry V. Zakrzewski, 114 Hillcrest Road, Frankfort, N.Y. 13340 Filed Aug. 7, 1967, Ser. No. 658,765 Int. Cl. Gllb 17/00 US. Cl. 2749 Claims ABSTRACT OF THE DISCLOSURE Direct drive for phonograph employing a circular sectioned O-ring belt of limited elasticity between a series of graduated diameter grooves on a motor shaft and a broad cylindrical skirt on the turntable acting as a driven pulley, and means to manually shift the belt between the grooves for drive speed variation.

This invention relates to sound reproducing apparatus, and more particularly to variable speed drives therefor.

In disk record phonographs, for example, a circular record holding table, rotated at a predetermined uniform speed, is provided. In order to handle records of different playing time and speeds, it is the practice to provide a drive from the driving motor in which provision is made for varying the speed of rotation of the turntable between speeds, for example, of 16%, 33 /3, 45 and 78 revolutions per minute. The speed shifting means and drive, for reducing the speed of a motor, for example, having an inherent speed of 3600 revolutions per minute, has generally included one or more counter shafts, friction drives and complicating means for changing the drive ratio.

The present invention is directed to apparatus employing a direct drive and including essentially a single moving part for effecting changes in speed. More particularly the drive includes a circular section drive belt riding on annular grooves on the motor shaft, and an annular channel, on the turn table, the drive belt having limited resilency, and non slipping characteristics in respect to the motor shaft spindle.

The above and other novel features of the invention will appear more fully hereinafter from the following detailed description when taken in conjunction with the accompanying drawings. It is expressly understood that the drawings are employed for purposes of illustration only and are not designed as a definition of the limits of the invention, reference being had for this purpose to the appended claims.

In the drawings wherein like reference characters indicate like parts:

FIGURE 1 is a fragmentary perspective view of a phonograph turntable, adjacent deck and motor drive, with the manual speed changer element removed.

FIGURE 2 is a sectional enlarged view of the speed changer,

FIGURE 3 is a sectional view taken on the broken line 3-3 of FIGURE 2.

Referring to the drawings there is shown a phonograph turntable 20 having a record centering pin 22, which table is rotatably mounted for rotation on a vertical axis on the lower deck 24 extending beneath the turntable. Mounted below the deck is a motor 26, which may be rigidly affixed to the deck by screws 28 threaded in the motor frame, and employing spacer sleeves 30 disposed between the deck and motor.

The motor shaft 32 projects upwardly and is extended sufficiently so that its upper end is laterally disposed in respect to the depending annular skirt 34 of the turntable 20. The end of the shaft is provided with a series of annular toroidal belt receiving grooves 38, 40, 42 and 44, of graduated diameters, selected in reference to the di- 3,445,117 Patented May 20, 1969 "ice ameter of the turntable skirt, and the motor speed, so as to provide satisfactory speed reductions. Thus by belt shifting, any one of a number of turntable speeds such as 16%, 33 /3, 45 or 78 revolutions per minute may be obtained. In order to provide uniformity of speed in the rotation of the turntable, motors of a synchronous character, having a speed of 3600 revolutions per minute may be employed, if desired, such motors being of relatively simple construction and available at low cost.

In practice the turntable skirt will preferably have a cylindrical belt receiving circumference 50 of an axial width commensurate with the axial belt shifting contemplated in regard to the motor shaft grooves 38, 40, 42 and 44, and will have slight annular flanges 52 and 54 above and below the cylindrical surface 50, to prevent the belt from leaving the drive surface 50. Provision for motor idling, without driving the turntable may be effected by applying a free running grooved sleeve 60 upon the motor shaft 32 just below the belt groove 44. Such sleeve may be made of nylon having antifriction characteristics in regard to the shaft metal. The sleeve may be confined between lock rings 62 and 64 seated in grooves in the shaft after positioning the sleeve. Preferably such sleeve will be of radially thin section to slip over the lower flange 45 of groove 44. On the other hand the several grooves 38, 40, 42 and 44 may be formed in a seperate element and applied over a reduced diameter portion of the motor shaft as by a press fit or otherwise, as will be well understood in the art.

The belt 35 employed to drive the turntable is preferably circular in section and of about A -inch diameter in cross section. The belt is preferably of neoprene and of limited resiliency, sufiicient to encompass any one of the grooves 38, 40, 42, and 44 with sufiicient frictional contact to drive the turntable without slippage. Belts of the type described may be of the O-ring type as are well known in the market.

In order to facilitate shifting of the belt to select a desired speed of rotation of the turntable, a manual shifter is provided. As shown, there is provided an upstanding tubular guide sleeve 80 having a mounting flange 82 af fixed to the deck 24. Such sleeve is provided with axially extending openings 84 and 86 of suflicient axial width to clear the reaches 88 and 89 of the belt 35. Slidable within the sleeve 80 is a manually shiftable tubular element 90 having a knurled knob 92, an arcuate slot 94 approaching 180 degrees in length, with rounded marginal edges 95 to engage the belt 35 without undue wear. Such shifter element is provided with a plurality of circular recesses 96 spaced in accordance with the spacing between the grooves 38, 40, 42 and 44 and the grooves of sleeve 60. Cooperating with said grooves, is a spring pressed detent ball 96 backed up by spring 97 in a radial socket 98 which may be formed integral with the sleeve 80. The lower end of the tubular member may have a split lock ring 100, applied after assembly to limit the upward movement of the shifter member.

In operation, it will be seen that by raising or lowering the shifter member, the belt 35 can be shifted to any one of the grooves whereby to idle, or drive the turntable at any desired speed.

In practice the root diameter of the groove 38 may be in the order of .036 inch to drive a turntable having a skirt somewhat larger than 7 inches in diameter at a speed or 16 /3 revolutions per minute from a motor having a speed of 3600 revolutions per minute, and the other diameters will be selected in proportion. The foregoing is merely representative since the skirt diameter, and motor speed may differ, particularly should a four pole synchronous motor be employed or frequencies other than 60 cycles be used.

While toroidal grooves for the circular sectional belt 35 are shown, such grooves might also be V grooves at about 120 degrees between faces in which case by calculation and test the correct diameters can be ascertained.

It will also be seen from the foregoing that the turntable drive, with a full range of speeds has been provided for through the use of a circular sectioned thin belt engaging the motor shaft and turntable only. Such belt, of neo- -prene and the like is practically incapable of transmitting irregular torque to the turntable, and insulates the turntable, against sound transmission from the motor which might otherwise spoil the true reproduction of the desired sound effects. Complete elimination of frictional drives employing rollers and the like, heretofore engaging the turntable skirt and likely to develop rumble is effected.

While a single form of the invention has been illustrated and described, it is to be understood that the invention is not limited thereto. As various changes in the construction and arrangement may be made without departing from the spirit of the invention, as will be apparent to those skilled in the art, reference will be had to the appended claims for a definition of the limits of the invention.

What is claimed is:

1. In a phonograph drive, a rotatably mounted turntable, having a depending annular skirt, and a drive motor laterally disposed with respect to the turntable skirt, and having a shaft end disposed in the approximate plane of the skirt, a plurality of belt grooves in said motor shaft end of graduated diameters, and a circular sectioned belt disposed in any one of the said grooves and extending around the turntable skirt said belt having limited resiliency for shifting to any one of the motor shaft grooves, the relation between the diameter of the shaft grooves, the diameter of the turntable skirt, and motor speed being such as to directly drive the turntable. at speeds correspending to the speeds of record tablets to be applied to the turntable, said shaft grooves being surrounded by a fixed sleeve having slots for the reaches of the belt, and a shiftable sleeve slidably disposed in the fixed sleeve and having an arcuate aperture of suflicient axial width and arcuate length to embrace the belt, and detent means for yieldingly holding the shiftable sleeve with its slot in the plane of any one of the shaft grooves, and for permitting 4 movement of the shiftable sleeve to shift the belt between adjacent grooves.

2. A phonograph drive in accordance with claim 1 wherein the annular skirt is cylindrical and provided with flanges spaced axially by an amount corresponding to the axial spacing between the motor shaft grooves.

3. A phonograph in accordance with claim 1 wherein one of the grooves is formed in a separate sleeve freely rotatable on the motor shaft.

4. In a phonograph drive, rotatably mounted turntable having a depending annular skirt, and a drive motor laterally disposed with respect to the turntable skirt, and having a shaft end disposed in the approximate plane of the skirt, a plurality of belt grooves in said motor shaft end of graduated diameters, and a circular sectional belt disposed in any one of the said grooves and extending around the turntable skirt said belt having limited resiliency for shifting to any one of the motor shaft grooves, the relation between the diameter of the shaft grooves, the diameter of the turntable skirt, and motor speed being such as to directly drive the turntable at speeds corresponding to the speeds of record tablets to be applied to the turntable, one of the grooves being formed in a separate sleeve freely rotatable on the motor shaft.

5. A phonograph drive in accordance with claim 4 wherein the annular skirt is cylindrical and provided with flanges spaced axially by an amount corresponding to the axial spacing between the motor shaft grooves.

References Cited UNITED STATES PATENTS 2,2445 06 6/ 1941 Staszkiewiecz 2749.1 3,047,297 7/ 1962 Drake 2749.1 3,248,961 5/1966 Bortzfield et a1. 74-2423 FOREIGN PATENTS 494,545 3/ 1930 Germany. 1,098,229 1/ 1961 Germany.

277,531 9/1930 Italy.

HARRY N. HAROIAN, Primary Examiner. 

